The muscle and principal neurovascular structures of the extremities are enclosed within fascial or osteofascial compartments. Increased pressure within these closed spaces may compromise the circulation and function of the enclosed tissues. The importance of this condition, known as the compartmental syndrome, lies in the relative frequency with which it complicates trauma and surgery and in its potential for causing permanent neuromuscular impairment. The clinical approach to this problem is hampered by the lack of objective criteria for its diagnosis and treatment. We propose to use an experimental model of the compartmental syndrome to investigate the effects of increased intracompartmental pressure on the metabolism and function of muscle and nerve. In this model the pressure within the anterior compartment of a rabbit may be raised and maintained at any desired level. The effect of this pressure elevation on the tissue p02 and pCO2 will be monitored by a Teflon catheter-mass spectrometer system. Neuromuscular function will be assayed by recording the mechanical contraction of the muscles of the compartment following stimulation of the peroneal nerve. Using these parameters the necessary conditions for the production of a compartmental syndrome will be investigated along with the criteria for the reversibility of this lesion. Surgical decompression is the essential treatment for the compartmental syndrome: when performed promptly the results are usually good. However, because serious complications may attend fasciotomy, nonoperative methods of treatment warrant investigation. The model compartmental syndrome will be used to study the effects of hyperoxygenation, isoproterenol, local cooling, and pulsed externally applied pressure on the pO2, pCO2, and function of compressed muscle. It is anticipated that these investigations will lead to a better definition of the pathophysiology of the compartmental syndrome and to more objective clinical guidelines for the diagnosis and management of this condition. A nonsurgical method of ameliorating compartmental syndromes may be identified.